Sodium Diuranate, Na2U2O7

Sodium Diuranate, Na2U2O7.6H2O, is prepared commercially as already described, and is generally known as "uranium yellow." It may be formed by adding excess of sodium hydroxide to a solution of a uranyl salt, and drying the resulting yellow precipitate in air. When dried over sulphuric acid it loses nearly all its water. It is obtained in the anhydrous condition by heating together uranyl chloride, sodium chloride, and ammonium chloride, or by strongly heating the hexahydrate.

The uranium yellow of commerce, which is used in staining and painting glass and porcelain and for making uranium glass, is obtained in two colours: light yellow, by decomposing the solution of sodium uranyl carbonate with sulphuric acid, and orange yellow, by decomposing with excess of sodium hydroxide.